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Abstract:

Techniques for manufacturing composite microstructures may be realized as
a three-dimensional structural component including first and second flat
structural regions and a joint region connecting the first and second
flat structural regions. The first, second, and joint regions can all
include an integral flexible layer comprising a first flexible material
that is fiber-reinforced and has a tear resistance greater than 10 N. At
least the first and second regions can each include a structural layer
comprising a second rigid material having greater stiffness than the
first flexible material.

Claims:

1. A three-dimensional structural component, comprising first and second
flat structural regions and a joint region connecting the first and
second flat structural regions; wherein the first, second, and joint
regions all include an integral flexible layer comprising a first
flexible material, the first flexible material being fiber-reinforced and
having a tear resistance greater than 10 N; and wherein at least the
first and second regions each include a structural layer comprising a
second rigid material having greater stiffness than the first flexible
material.

2. The component of claim 1, wherein the joint region does not include a
structural layer comprising the second rigid material, and wherein the
joint region is configured to be folded such that the first and second
flat structural regions are non-coplanar.

3. The component of claim 1, wherein each of the first and second regions
each include a second rigid layer such that the flexible layer is
sandwiched between two rigid layers.

4. The component of claim 1, wherein the two rigid layers for each of the
first and second regions are composed of the same rigid material.

5. The component of claim 1, wherein the integral flexible layer adheres
to the structural layers of the first and second regions by means of a
pressure-activated adhesive.

6. The component of claim 1, wherein the integral flexible layer adheres
to the structural layers of the first and second regions by means of a
thermal adhesive.

7. The component of claim 1, wherein the first flexible material has a
thickness of between 15 and 150 microns.

8. The component of claim 1, wherein the first flexible material has a
melting point above 200.degree. C.

9. The component of claim 1, wherein the first flexible material has an
activation energy above 35 mN/m.

10. The component of claim 1, wherein the first flexible material is
ripstop nylon.

11. A method for manufacturing a three-dimensional structural component,
comprising: positioning an integral flexible layer comprising a first
flexible material adjacent to an integral structural layer comprising a
second rigid material, the first flexible material being fiber reinforced
and having a tear resistance greater than 10 N; applying pressure to
adhere the integral flexible layer to the integral structural layer;
cutting the integral structural layer into first and second structural
layers while leaving the integral flexible layer intact, forming first
and second structural regions connected by a joint region; and folding
the joint region such that the first and second structural regions are
non-coplanar.

12. The method of claim 11, wherein positioning the flexible layer
includes positioning the flexible layer between two integral structural
layers; and wherein applying pressure adheres both of the integral
structural layers to either side of the flexible layer.

13. The method of claim 11, further comprising: applying heat to adhere
the integral flexible layer to the integral structural layer.

14. The method of claim 11, further comprising: cutting out a
three-dimensional structural component from the integral layers, the
three-dimensional component including the first and second structural
regions and the joint region.

16. The method of claim 11, wherein the first flexible material has a
thickness of between 15 and 150 microns.

17. The method of claim 11, wherein the first flexible material has a
melting point above 200.degree. C.

18. The method of claim 11, wherein the first flexible material has an
activation energy above 35 mN/m.

19. The method of claim 11, wherein the first flexible material is
ripstop nylon.

Description:

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to U.S. Provisional Application
No. 61/976,029, filed Apr. 7, 2014, which is incorporated by reference in
its entirety as though fully disclosed herein.

TECHNICAL FIELD

[0002] This application relates generally to prototyping and
manufacturing, and more specifically to composite materials.

BACKGROUND

[0003] Smart Composite Microstructures (or SCM) is a manufacturing process
that was originally developed at UC Berkeley for the construction of
robots at the millimeter scale. This process employs two rigid layers and
a flexible layer in a laminate structure to form flexure joints, which
are frictionless and thus scale well to small structures.

[0004] The structure is generally cut using a laser cutter, but many
cutting methods could be appropriate. A flat structure is the product,
which must be folded into a final three dimensional shape to create a
useful device. Older SCM designs are difficult to assemble, due to having
small parts, a lack of alignment features, and many parts. Construction
often requires specialized tools, such as tweezers, fine knives), and
specialized glue.

[0005] In the SCM process, a joint is formed in a composite by combining
rigid and flexible layers, and selectively cutting away parts of the
rigid layer. This is done in a multi-step process, shown below. Existing
SCM flexible have been made of mylar (PET), which tears easily and does
not last under normal use.

[0006] A need therefore exists for an improved material which is more
appropriate and resilient under the conditions of SCM manufacture,
assembly, and use.

SUMMARY

[0007] In accordance with the disclosed subject matter, systems and
methods are described for a manufacture of composite microstructures.

[0008] In one embodiment, the techniques may be realized as an apparatus
including first and second flat structural regions and a joint region
connecting the first and second flat structural regions. The first,
second, and joint regions can all include an integral flexible layer
comprising a first flexible material that is fiber-reinforced and has a
tear resistance greater than 10 N. At least the first and second regions
can each include a structural layer comprising a second rigid material
having greater stiffness than the first flexible material.

[0009] In accordance with other aspects of this embodiment, the joint
region may not include a structural layer comprising the second rigid
material. The joint region can be configured to be folded such that the
first and second flat structural regions are non-coplanar.

[0010] In accordance with other aspects of this embodiment, the first and
second regions can each include a second rigid layer such that the
flexible layer is sandwiched between two rigid layers.

[0011] In accordance with other aspects of this embodiment, the two rigid
layers for each of the first and second regions can be composed of the
same rigid material. The integral flexible layer can adhere to the
structural layers of the first and second regions by means of a
pressure-activated adhesive.

[0012] In accordance with other aspects of this embodiment, the integral
flexible layer can adhere to the structural layers of the first and
second regions by means of a pressure-activated adhesive.

[0013] In accordance with other aspects of this embodiment, the integral
flexible layer can adheres to the structural layers of the first and
second regions by means of a thermal adhesive.

[0014] In accordance with other aspects of this embodiment, the first
flexible material can have a thickness of between 15 and 150 microns.

[0015] In accordance with other aspects of this embodiment, the first
flexible material can have a melting point above 200° C.

[0016] In accordance with other aspects of this embodiment, the first
flexible material can have an activation energy above 35 mN/m.

[0017] In accordance with other aspects of this embodiment, the first
flexible material can be ripstop nylon.

[0018] In accordance with another embodiment, the techniques may be
realized as an process for manufacture including the steps of positioning
an integral flexible layer comprising a first flexible material adjacent
to an integral structural layer comprising a second rigid material, the
first flexible material being fiber reinforced and having a tear
resistance greater than 10 N; applying pressure to adhere the integral
flexible layer to the integral structural layer; cutting the integral
structural layer into first and second structural layers while leaving
the integral flexible layer intact, forming first and second structural
regions connected by a joint region; and folding the joint region such
that the first and second structural regions are non-coplanar.

[0019] In accordance with other aspects of this embodiment, the method may
further include applying heat to adhere the integral flexible layer to
the integral structural layer.

[0020] In accordance with other aspects of this embodiment, the method may
further include cutting out a three-dimensional structural component from
the integral layers, the three-dimensional component including the first
and second structural regions and the joint region. In accordance with
further aspects of this embodiment, cutting out the three-dimensional
structural component can use laser cutting.

[0021] In accordance with other aspects of this embodiment, the first
flexible material can have a thickness of between 15 and 150 microns.

[0022] In accordance with other aspects of this embodiment, wherein the
first flexible material can have a melting point above 200° C.

[0023] In accordance with other aspects of this embodiment, wherein the
first flexible material can have an activation energy above 35 mN/m.

[0024] In accordance with other aspects of this embodiment, the first
flexible material can be ripstop nylon.

[0025] The present disclosure will now be described in more detail with
reference to particular embodiments thereof as shown in the accompanying
drawings. While the present disclosure is described below with reference
to particular embodiments, it should be understood that the present
disclosure is not limited thereto. Those of ordinary skill in the art
having access to the teachings herein will recognize additional
implementations, modifications, and embodiments, as well as other fields
of use, which are within the scope of the present disclosure as described
herein, and with respect to which the present disclosure may be of
significant utility.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Various objects, features, and advantages of the disclosed subject
matter can be more fully appreciated with reference to the following
detailed description of the disclosed subject matter when considered in
connection with the following drawings, in which like reference numerals
identify like elements.

[0027] FIG. 1 is a cross-sectional view of the flexible and structural
layers of a component in accordance with some embodiments.

[0034] FIG. 5B illustrates the two three-dimensional components from FIG.
3A, cut and folded and attached according to some embodiments.

[0035] FIGS. 6A and 6B show cross-sectional views of the insertion of a
fastener to connect two components according to some embodiments.

DESCRIPTION

[0036] In the following description, numerous specific details are set
forth regarding the systems and methods of the disclosed subject matter
and the environment in which such systems and methods may operate, in
order to provide a thorough understanding of the disclosed subject
matter. It will be apparent to one skilled in the art, however, that the
disclosed subject matter may be practiced without such specific details,
and that certain features, which are well known in the art, are not
described in detail in order to avoid complication of the disclosed
subject matter. In addition, it will be understood that the embodiments
described below are only examples, and that it is contemplated that there
are other systems and methods that are within the scope of the disclosed
subject matter.

[0037] The invention presented here employs multiple features not
previously used in SCM designs to allow easy, rapid folding without the
use of specialized tools or adhesives. The invention is an integrated
design that includes lap joints, press fits, tabs, and structural
spring-loading. These features are designed into the structure of the
composite itself, not using common methods as in conventional
manufacturing processes, which may also create lap joints and press fits.

[0038] In the SCM process, a joint is formed in a composite by combining
rigid and flexible layers, and selectively cutting away parts of the
rigid layer ("flexure cuts"). A resulting component 100 having these
layers is illustrated in FIG. 1. The component 100 includes first and
second structural regions 102a and 102b, each of which is composed of a
flexible layer 104 sandwiched between two rigid layers 106, 108. Between
the two structural regions is the joint region 110, which includes the
flexible layer 104 but not the rigid layers 106, 108. The flexible layer
104 therefore forms a continuous layer of material across all regions of
the component 100, while the rigid layers 106 and 108 are removed from
the joint region 110 to allow it to act as a flexible joint.

[0039] FIGS. 2A and 2B show one example of a simple three-dimensional
component 200 in accordance with the invention. The component 200, as
illustrated in FIG. 2A, may be cut from a sheet including both rigid and
flexible layers. The outer edges 202 represent cuts through all three
layers in order to form the pattern of the component 200, while the inner
edges 204, shown in bold, are made by removing only the rigid layers as
described above with respect to FIG. 1 and joint region 110. These
"flexure cuts" result in joint regions 204 where the component 200 can be
folded in order to form faces 206a-e oriented in different planar
directions, as illustrated in FIG. 2B. By folding the faces 206a-d at the
joint regions 204, the component yields a box shape with one open side.

[0040] As a further example, FIGS. 3A and 3B illustrate a chassis 300 for
a microrobot which is, again, cut from a sheet having multiple layers
with full outline cuts and internal flexture cuts as shown in regular and
bold lines, respectively, in FIG. 3A. Once the pattern is cut from the
sheet, the component 300 can be folded at the joint regions to form the
three-dimensional chassis shape as shown in FIG. 3B. Other components can
be cut and added to the chassis using the same technique.

[0041] Manufacturing the component may involve the application of a
thermal adhesive and one or more lamination steps, including the
application of pressure and/or heat to the layers such that they properly
adhere. The particulars of the lamination process may depend on the
materials as further explained below.

[0042] An example process 400 for manufacturing a component in accordance
with embodiments of the present invention is illustrated by the flowchart
of FIG. 4. One of ordinary skill in the art will recognize that this
manufacturing process is exemplary and that some variation in the method
will be known to yield similar results.

[0043] To begin the manufacturing process, adhesive is added to each rigid
layer (402). The adhesive may be selected for its bonding properties for
the materials used for the rigid and flexible layers, as further outlined
below. The adhesive may be pressure and/or heat sensitive;
correspondingly, heat and/or pressure may be applied to each rigid layer
in order to apply the adhesive. In some implementations, a particular
amount of time is based to allow the adhesive to wet each rigid layer,
but not so much time that the adhesive dries before the addition of the
flexible layer as described below.

[0044] Flexure cuts are made in each rigid layer (404). These cuts may be
made, for example, by the use of a laser cutter or other precision
cutting technique. In some implementations, the system may take advantage
of the fact that flexure cuts in the two rigid layers will generally be
mirror images, as illustrated in FIG. 1. The two layers may therefore, in
some implementations, be positioned roughly parallel to each other and a
single cut applied across both layers.

[0045] The rigid layers, now with flexure cuts, are positioned on either
side of the flexible layer (406). Various techniques may be used to
assure alignment of the layers such that the flexure cuts are actually
mirrored on either side of the flexible layer. In some implementations,
machine vision or other techniques may be used to assure precise
positioning between layers.

[0046] Further heat and/or pressure is applied to the sandwiched layers in
order to fully bond the rigid and flexible layers together (408). Various
quality control practices may be involved to make sure that the layers
fully bond and will not layer delaminate, although the proper selection
of materials (as further described below) should help to reduce such
defects.

[0047] Once the layers are bonded together, the outline cuts are made
through all three layers (410). This may again be done on a laser cutter
or other precision material. This cutting step may again involve aligning
the layers according to the position of the flexure cuts so that the
outline and flexure cuts create the appropriate shapes in the resulting
component.

[0048] Efficient manufacturing and handling of these components require
careful selection of materials for the flexible and rigid layers. Because
the component joints include the flexible layer alone, this layer must be
selected not only for flexibility, but for strength and durability as
well. SCMs have customarily used sheets made from polyethylene
terephthalate resin ("PET"). While adequate in certain respects, PET
fails to meet the materials criteria for the present invention as
explained below.

[0049] Tear strength. The flexible layer material needs to have
sufficiently high tear strength to resist tearing at the joints, which
are put under stress when the mechanism operates. In order to reliably
operate without tearing during regular use, the flexible material used in
the components should generally be able to withstand upwards of 10 N of
force before tearing. A material with a tear resistance above 10 N will
withstand normal handling and operation. If the flexible material has a
tear resistance significantly below 10 N, the chances of tearing during
normal assembly and use rises greatly.

[0050] A standard sheet of PET resin of 2 mil thickness has a tear
resistance on the order of 0.3 to 0.5 N. This is well below the desired
threshold, and represents a significant likelihood of tearing during use.
In contrast, a sheet of ripstop nylon easily withstands 30 N or more of
force before tearing. Thus, fiber-reinforced thermoplastic such as
ripstop nylon is greatly preferred over traditional materials for
resilience in assembly and handling.

[0051] Thickness. The thickness of the flexible layer greatly affects both
the bend radius and bending stiffness of the flexible material. Ideally
the thickness should allow for a characteristic "springiness" in the
joint regions such that the pieces can be bent into their
three-dimensional configuration and then remain in that shape thereafter.

[0052] If the bend radius is too high, then the mechanism will not fold
properly into its intended three-dimensional shape. Further, for systems
that are mechanically actuated (such as microrobots), an excessive
stiffness in the joints due to and overly thick flexible layer may reduce
movement efficiency and require excessive energy output in order to
operate.

[0053] On the other hand, a thickness below the effective range may be too
yielding and not hold shape nor provide sufficient resistance to movement
for sufficient structural support to the three-dimensional components. A
thickness on the order of 15 to 150 microns provides the appropriate
flexibility and resilience.

[0054] Various fiber-reduced thermoplastics, most notably ripstop nylon,
are provided in the 25-100 micron thickness range. These thermoplastics
are therefore acceptable with respect to their thickness as candidates
for the flexible layer material.

[0055] Melting temperature. During initial manufacture of the
three-dimensional component, heat is often applied to laminate the layers
together. Further, laser cutting is often the preferred method for making
the outline cuts to separate the component die from the fabric sheet.
During both these procedures, it is greatly preferred that the layer
materials have melting temperatures in excess of 200° C. so as not
to deform during lamination and cutting. Both customarily-used PET and
certain fiber-reinforced thermoplastics, such as ripstop nylon, have
melting points between 250° C. and 275° C., and so are
therefore appropriate candidates for the flexible material based on this
measure.

[0056] Adhesion/surface energy. The flexible material must have sufficient
surface energy such that the adhesive can properly bond the flexible
layer to the rigid layers during lamination. Insufficient adhesion can
result in delamination, either during the initial manufacturing process
or later during handling. Surface energy at or above 35 mN/m is
sufficient for the bonding agents most typically used. Both PET and
ripstop nylon have surface energies measured in excess of 40 mN/m and so
bond adequately under manufacturing conditions to avoid delamination.

[0057] Table I below shows the comparison of four materials based on the
properties noted above: basic extruded polyethylene terephthalate resin
sheet ("PET"), ripstop nylon, spunbond polyolefin fiber (trade name
TYVEK®) and fiber-reinforced woven polyester fabric (trade name
DACRON®). One of ordinary skill the art will recognize that other
materials could be evaluated on this same basis.

[0058] From the above table, PET is not tear resistant enough, and Tyvek
is wholly unsuited. Ripstop nylon matches all four criteria, and is
therefore an example of an appropriate material for use in the flexible
layer of the components. Ripstop Dacron, which is woven rather than
extruded plastic, also matches all four criteria and would therefore be
suitable as the material for the flexible layer.

[0059] The increased resilience and durability of components using
materials meeting the above criteria allows for three-dimensional
components to be attached together in a variety of ways. In some
implementations, components are joined together by means of tab-and-slot
connectivity between pieces, the resilient joint allowing for these
pieces to be securely joined together by hand. FIGS. 5A and 5B illustrate
two components 500a,500b which, when folded, can fit together by means of
tabs 502 fitting into cut slots 504. FIG. 5B illustrates the two
components attached together.

[0060] In addition to using the properties of the components themselves to
allow for integral attachment of pieces, fasteners may also be added in
some cases. SCM customarily used glue to attach pieces, but this solution
is imprecise and tends to wear quickly with normal use. A superior method
is to use hard fasteners such as the plastic rivets 600 shown in FIGS. 6A
and 6B. What are depicted are button-type rivets 600, which are designed
to be deployed by applying a downward force F onto the head as shown in
FIG. 6A. The rivets 600 provide a secure, permanent connection when
placed. As illustrated in FIG. 6A, a rivet 600 can connect a first
component 602a to a second component 602b by placement in a hole of
proper diameter (the necessary diameter D1 of the hole will depend on the
size of the rivet 600). The rivets 600 can be constructed of any
appropriate lightweight material, such as aluminum or thermoplastic.

[0061] It is to be understood that the disclosed subject matter is not
limited in its application to the details of construction and to the
arrangements of the components set forth in the following description or
illustrated in the drawings. The disclosed subject matter is capable of
other embodiments and of being practiced and carried out in various ways.
Also, it is to be understood that the phraseology and terminology
employed herein are for the purpose of description and should not be
regarded as limiting.

[0062] As such, those skilled in the art will appreciate that the
conception, upon which this disclosure is based, may readily be utilized
as a basis for the designing of other structures, methods, and systems
for carrying out the several purposes of the disclosed subject matter. It
is important, therefore, that the claims be regarded as including such
equivalent constructions insofar as they do not depart from the spirit
and scope of the disclosed subject matter.

[0063] Although the disclosed subject matter has been described and
illustrated in the foregoing exemplary embodiments, it is understood that
the present disclosure has been made only by way of example, and that
numerous changes in the details of implementation of the disclosed
subject matter may be made without departing from the spirit and scope of
the disclosed subject matter, which is limited only by the claims which
follow.